Multistimuli-Responsive Properties of Aggregated Isocyanide Cycloplatinated(II) Complexes

Here, we describe the neutral cyclometalated tert-butylisocyanide PtII complexes, [Pt(C∧N)Cl(CNBut)] 1, the double salts [Pt(C∧N)(CNBut)2][Pt(C∧N)Cl2] 2, and the cationic complexes [Pt(C∧N)(CNBut)2]ClO43 [C∧N = difluorophenylpyridine (dfppy, a), 4-(2-pyridyl)benzaldehyde (ppy-CHO, b)]. A comparative study of the pseudopolymorphs 1a, 1a·CHCl3, 1b, 1b·0.5Toluene, 1b·0.5PhF, and 3a·0.25CH2Cl2 reveals strong aggregation through Pt···Pt and/or π···π stacking interactions to give a variety of distinctive one-dimensional (1D) infinite chains, which modulate the photoluminescent properties. This intermolecular long-range aggregate formation is the main origin of the photoluminescent behavior of 1a and 1b complexes, which exhibit highly sensitive and reversible responses to multiple external stimuli including different volatile organic compounds (VOCs), solvents, temperatures, and pressures, with distinct color and phosphorescent color switching from green to red. Furthermore, complex 1b undergoes supramolecular self-assembly via Pt···Pt and/or π···π interactions into a polymer thin polystyrene (PS) film 10 wt % in response to toluene vapors, and 3a exhibits vapochromic and vapoluminescent behavior. Theoretical simulations on the dimer, trimer, and tetramer models of 1a and 1b have been carried out to get insight into the photophysical properties in the aggregated solid state.


Preparation of [Pt(ppy-CHO)(CNBu t ) 2 ]ClO 4 (3b)
. This compound was prepared as a pale yellow solid (0.330 g, 83 %) following the procedure described for 3a using a yellow X-ray Crystallography. Details of the X-ray analyses are summarized in Tables S1-S5.
Yellow (1a and 1b), red (1b·0.5Toluene and 1b·0.5Fluorobenzene (PhF)) and pale S7 yellow (3a·0.25CH 2 Cl 2 ) crystals were obtained by slow diffusion of n-hexane into solutions of the complexes in CH 2 Cl 2 (1a, 3a·0.25CH 2 Cl 2 ), THF (1b), toluene (1b·0.5Toluene) and fluorobenzene (1b·0.5PhF) at room temperature. Slow evaporation of a CHCl 3 solution of 1a·CHCl 3 (298 K) gave pale-yellow crystals. The diffraction data were collected using graphite-monochromatic Mo-K  radiation with a Bruker APEX-II diffractometer at 298 K (1a, 1a·CHCl 3 and 3a·0.25CH 2 Cl 2 ) and 100 K (1b, 1b·0.5Toluene and 1b·0.5PhF) using the APEX-II software. The structures were solved with the WINGX program suite 5 by intrinsic phasing using SHELXT program 6 and refined by full-matrix least squares on F 2 with SHELXL. 7 All non-hydrogen atoms were assigned anisotropic displacement parameters. All the hydrogen atoms were constrained to idealized geometries and assigned isotropic displacement parameters equal to 1.2 times the U iso value of their respective attached carbon for the aromatic and CH 2 hydrogen atoms, except those of methyl groups, which were fixed to 1.5 times the U iso value of their attached carbons. For 1a·CHCl 3 , 1b·0.5Toluene, 1b·0.5PhF and 3a·0.25CH 2 Cl 2 , one CHCl 3 molecule, a half toluene and fluorobenzene molecule and a 0.25 dichloromethane molecule, respectively, were properly resolved from the difference density map. During the refinement, several restraints and constraints had to be applied. DFIX, FLAT, EADP, RIGU and TWIN/BASF instructions were employed to model the molecules' geometry and temperature parameters. For 1a, the planarity of the disordered phenyl ring fragment was reached with FLAT and EADP. For 1a·CHCl 3 , the tertbutyl group was modelled as a rotational disorder over two positions in 50:50 ratios. The 3a·0.25CH 2 Cl 2 data included instructions DFIX restraining two C-C bonds of two tertbutyl and three Cl-O bonds in perchlorate anions to have equal lengths. Moreover, four tertbutyl moieties EADP constrains were applied to chemically equivalent atoms. One of the perchlorate anion (ClO 4 ) was obtained as a distorted fragment and RIGU restraints was applied to the U if coefficients of this anion. In 1a, 1b·0.5Toluene and 1b·0.5PhF, the twinning was treated with the appropriate TWIN law and BASF parameter to refine the twin components due to a small but non-zero Flack parameter.
Computational details. Calculations were carried out with the Gaussian 16 package 8 for compounds 1a, 1b and 3a, using Becke´s three-parameter functional combined with Lee-Yang-Parr´s correlation functional (B3LYP). 9 Optimizations on the singlet state (S 0 ) were performed using as a starting point the molecular geometry obtained through X-ray diffraction analysis. No negative frequency was found in the vibrational frequency S8 analysis of the final equilibrium geometries. The basis set used was the LanL2DZ effective core potential for Pt and 6-31G(d,p) for the ligand atoms. 10 DFT and TD-DFT calculations were carried out using the polarized continuum model approach 11 (PCM) implemented in the Gaussian 16 software, in the presence of dichloromethane. To study the packing interaction, the dimeric, trimeric and tetrameric 1a and 1b geometries in the ground (S 0 ) and the first triplet excited (T 1 ) were optimized in gas phase based on 1a and 1b·0.5Toluene crystals structures by using a pair of symmetry-related platinum(II) moieties (dimers), trimers and tetramers with the shortest intermolecular Pt···Pt distance.
In 1b·0.5Toluene, as the solvated molecules of toluene were found to exert insignificant influence on the calculated results, the calculations were performed without considering the toluene molecules. The calculations were carried out through the Grimme approach using atom pair-wise additive schemes using dispersion-corrected B3LYP-D3 method to elucidate the dispersion effects for non-bonding interaction. 12 The emission energy was calculated as the difference of the optimized T 1 and S 0 state in the optimized T 1 geometry (adiabatic electronic transition). The results were visualized with GaussView 6. Overlap populations between molecular fragments were calculated using the GaussSum 3.

Figure S37
. Thermogravimetric analysis (scan rate of 5 °C min −1 ) of the pristine solid 1b after exposure to saturated vapors of toluene, revealing its composition as 1b·0.5Toluene. Figure S38. Normalized emission and excitation spectra of 1b·0.5Toluene after one month exposed to air at 298 K. Figure S39. Images of the red crystals in the PS film (10%) of 1b, obtained by exposition to toluene, after two months on standing at air. The left image has a magnification of 40x, while right image has a magnification of 10x.
S46 Figure S40. Normalized emission spectra of 2a (λ ex 550 nm 298 K, λ ex 580 nm 77 K) (a) and 2b (λ ex 515 nm 77 K) (b) in solid state. Figure S41. Emission spectra in solid state at 298 K and 77 K of 3a-pristine and 3a·0.25CH 2 Cl 2 (a) and 3b-pristine (b). Figure S42. a) Normalized excitation and emission spectra of vapochromic response of 3apristine in solid state at 298 K (λ ex 420-430 nm). b) Normalized absorption spectra calculated from their reflectance spectra in the solid state. Figure S43. a) Normalized emission and excitation spectra of 3a-acetone (a) and 3a-CHCl 3 (b) in solid state at 77 K.  Figure S44. Optimized geometries of [1b] 4 model at the S 0 and T 1 states. Contour plots of HOMO and LUMO at the S 0 and spin density at the T 1 optimized geometries [B3LYP/ 6-31G(d,p)].